The present invention is directed to a method of obtaining a substantially void free interface between a substrate surface having a raised relief and a photopolymerizable dry film applied thereto. More specifically the present invention is particularly adapted to application of a solder mask in manufacture of a printed circuit board.
Friel U.S. Pat. No. 4,127,436 discloses a process for applying under a vacuum a photoresist-forming layer to a substrate surface wherein it is stated that a laminate without entrapped air bubbles is formed.
Oizuma U.S. Pat. No. 4,388,129 discloses a method for impregnating a porous fibrous substrate with a solvent-free liquid resin, allowing substantially all entrapped air bubbles to disappear and curing the combination. The air bubbles can be eliminated by allowing the impregnated article to stand for a sufficient period of time which may be shortened by applying ultrasonic waves, by placing the green laminate in compressed air or by using degassed liquid resin.